For the time being, it is common to provide card operated locks with an emergency opening mechanism. This is a demand from some users and often from the fire department. The fire authorities will in some cases and in some fields of applications, e.g., hotels, often demand a mechanical opening possibility which is simple and well known, and which overrides card readers and electronics.
This emergency opening is often made as a lock cylinder of a known conventional type. In hotels, this lock cylinder is often a type which is relatively difficult to pick, but which can be opened with a main key, a so-called master key or floor key.
Such a system has weak points which are hard to avoid. Because no chain is stronger than the weakest joint, it follows that the possibility to pick the lock, which is very low for the card reader, is put back to "old fashion" level for the emergency opening mechanism. Several picking methods are experienced. In some cases the burglar has had success in picking the lock cylinder, or at least in attempting to pick it. However, in several cases the following method is used: a burglar rents a room in the hotel in a legal manner. During the night he removes the lock cylinder and replaces it with another with the same appearance. The staff will not notice this, because this emergency opening is never or very rarely used. The burglar can then bring the lock cylinder to his home and undisturbed analyse it and determine the shape of the master key. He may then visit the hotel, and by use of this key he is able to make to lot of damage by stealing from the rooms. The hotel will be forced to replace all compromised lock cylinders.